Automotive Engineer

It’s difficult to drive around town without seeing either a Toyota Prius or a Honda Insight. The two OEMs are producing more and more hybrid vehicles as they try to reduce CO2 emissions. And other carmakers are following.

But the technology isn’t perfect. Battery technology especially needs refinement.

There’s no escaping the fact that batteries are heavy. Even the Prius battery weighs 50kg. Flywheel hybrid systems that do away with that weight could improve vehicle efficiency even more, while still benefiting from electrification of the powertrain.

The technology has come a long way since it was first used in trams and buses 60 years ago. 

The old 500kg flywheel spinning at 2,000rpm has been replaced by something that weighs 5kg and spins at up to 60,000rpm.

The technology has already been out on the track in Formula One and in the Porsche 911 GT3 R Hybrid at the Nürburgring 24-hour race. But it isn’t just motor racing where the technology can be used. Testing is being conducted to see how beneficial it could be on a road car.

Williams designed the hybrid system for the Porsche, but automotive supplier Flybrid is developing a version for road cars. Jon Hilton, managing partner at Flybrid, says: “I think Williams have done a really good thing for flywheel technology. It’s precisely where cars will be in 10 years’ time, when the car engine has been heavily downsized, and performance is boosted with a hybrid system.”

Hilton may have a vested interest in the technology but as a means of helping OEMs to reduce their CO2 emissions it’s worth looking at.

“You’re going to have to do kinetic energy recovery to get anywhere near the 95g CO2 average in 2020,” he says.